18.104.22.168. Synthesis for the purpose of identification
Although the study of retention time and mass spectrum normally provides reliable data for the identification, injection and coinjection represent the definitive proof of the identity. If standard compounds are not readily available they have to be synthesized using organic chemistry techniques that are outside the purpose of this review. Some of these techniques have been used extensively; in particular the Wittig reaction for the synthesis of unsaturated HC. In a few cases suitable alternatives (e.g. the partial hydrogenation of the corresponding alkyne obtained by alkylation of a convenient terminal alkyne with 1-bromoalkanes of suitable chain length according to Sonnet, 1984) have been used giving excellent results (Nazzi et al., 2002).